This invention relates generally to flow control valves and more particularly to such valves that provide for continuity in valve sealing action upon exposure to fire or any like, extraordinary thermal event.
Ball valves and butterfly valves used in regulating the flow through pipes carrying petroleum hydrocarbons and like fluids commonly incorporate elastomeric seals fabricated from such materials as fluorocarbon polymers, polyurethanes, and various olefinic polymers and copolymers. Even the more thermally stable of these materials fail in their valve sealing function at temperatures in excess of about 650.degree. F. In my U.S. Pat. No. 3,537,682, I have disclosed inorganic valve seals which function effectively at temperatures on the order of 1200.degree.-1300.degree. F. However, the latter seals are costly and are less desirable than elastomeric seals for use at more conventional operating temperatures. In addition, it has been known heretofore to construct flow control valves with auxiliary metal seats or seals which are normally disposed in approximate contact with the valve element and which rely primarily upon thermal expansion during a fire or the like in order to effect a safety sealing action. Under normal conditions these seals will not provide an effective seal, as to do so would require a degree of engagement with the movable valve element that would impede the desired ease of valve operation. Accordingly, upon cooling down after the fire has been struck, these prior art metal seals will contract and assume their normal position, resulting in an interuption of the contact with the valve element, creating a danger of leakage.
It is, therefore, an important object of my present invention to provide a flow control valve with an auxiliary seal that affords continued sealing action after once having been exposed to extraordinary high temperatures and regardless of subsequent cooling.
A more general object of the invention is to provide a new and improved flow control valve having fire safety features.
Another object of the invention is to provide a fire safety valve which functions regardless of the direction of flow pressure.
These and other objects and features of the invention will become more apparent upon a consideration of the following descriptions.